Dissertations / Theses on the topic 'Micro-Generators'

The key question this thesis aims to address is to what extent can micro-generation sources contribute to the carbon emission reduction targets set by the UK government. The operational emissions of micro-CHP capable micro-generators were examined against the UK grid electricity and gas boiler heat. Fossil and biomass fuels were considered. The life-cycle emissions associated with the manufacturing, transport and disposal of micro-generators were calculated. Case studies were constructed, based on the literature. It was found that emissions associated with domestic electrical and thermal demand would be reduced significantly. A Virtual Power Plant (VPP) was defined for aggregating micro-generators, using micro-generation penetration projections for the year 2030 from the literature. An optimisation problem was described, where the goal was to minimise the VPP carbon emissions. The results show the amount of emissions that would potentially be reduced by managing an existing micro-generation portfolio in a VPP. An Environmental Virtual Power Plant (EVPP) was defined, for controlling micro-generator carbon emissions. A multi-agent system was designed. The principle of operation resembles an Emissions Trading Scheme. Emission allowances are traded by the micro-generators, in order to meet their emissions needs. Three EVPP control policies were identified. Fuzzy logic was utilised for the decision making processes. Simulations were performed to test the EVPP operation. The main benefit for the micro-generators is the ability to participate in markets from which they would normally be excluded due to their small size. The multi-agent system was verified experimentally using micro-generation sources installed in two laboratories, in Athens, Greece. Two days of experiments were performed. Results show that system emissions have been successfully controlled, since only small deviations between desired and actual emissions output were observed. It was found that Environmental Virtual Power Plant controllability increases significantly by increasing the number of participating micro-generators.

Silicon and silicon-germanium nanostructures were grown, integrated, optimized and characterized for their application in thermoelectric generation. Specifically two kinds of nanostructures were worked: silicon and silicon-germanium nanowire arrays (Si/Si-Ge NW) and polycrystalline silicon nanotube fabrics (pSi NT). The results are dived in four chapters. Chapters 3, 4 and 5 deal with Si/Si-Ge NWs, while chapter 6 presents the pSi NT fabrics. In Chapter 3 the growth and integration of Si/Si-Ge NWs was studied, in order to optimize their properties for thermoelectric application in micro-thermoelectric generators (µTEG). First, the methods for depositing gold nanoparticles prior to NW growth were studied. Second, the growth of NWs from the gold nanoparticles in a Chemical Vapour Deposition (CVD) process was comprehensively studied and optimized for subsequent integration of NWs in µTEGs, both of Si and Si-Ge. All important properties – NW length, diameter, density, doping and alignment – could be controlled by tuning the seeding gold nanoparticles and the process conditions, namely temperature, pressure, flows of reactants and growth time. Finally, integration was demonstrated in micro-structures for thermoelectric generation and characterization. The optimization process yielded to fully integrated thermoelectric Si/Si-Ge NW arrays with diameters and densities of ~100 nm and 5 NW/µm2 respectively. In Chapter 4 the Si NWs were thermoelectrically characterized. The Seebeck coefficient, electrical conductivity and thermal conductivity of arrays and single Si-NWs were measured in microstructures devoted to characterization comprising NWs integrated as in final µTEG application. Additionally a novel atomic force microscope based method for determination of thermal conductivity was explored. Then the results were discussed comparing them with existing literature. A ZT of 0.022 was found at room temperature, revealing an improvement of factor 2-3 with respect to bulk. In Chapter 5 The harvesting capabilities of µTEGs with integrated Si/Si-Ge NWs was assessed. The thermal gradient and the power of the µTEGs was assessed for two generation of devices and for two thermoelectric materials, namely Si and Si-Ge NWs, which were integrated for the first time in functional generators. Also a study on heat sinking and convection effects was conducted adding insight towards further device improvement. Finally, the results were discussed and compared with literature. The maximum power densities attained were 4.5 µW/cm2 for the Si NWs and 4.9 µW/cm2 for the Si-Ge NWs while harvesting over surfaces at 350 ºC. Chapter 6 deals with pSi NT fibers. First this new material concept and the growth route are presented, showing the fabrication steps and the control of the resulting properties by CVD method. Then the material is thermoelectrically characterized, by measuring its Seebeck coefficient and electrical and thermal conductivities up to 450 ºC. A ZT of 0.12 was found, doubling the optimally doped bulk at this temperature. Finally a proof of concept was demonstrated by assessing the thermal harvesting capabilities of the material on top of hot surfaces. A maximum of 3.5 mW/cm2 was attained at 650 ºC.
Los materiales termoeléctricos permiten la conversión de calor a electricidad y viceversa. Esto permite explotar el efecto termoeléctrico en generadores termoeléctricos, capaces de extraer energía térmica de fuentes calientes y convertirla a electricidad útil. Estos generadores presentan grandes ventajas, como su falta de piezas móviles – y por ende necesidad de mantenimiento alguna – y su total escalabilidad, que permite cambiar su tamaño sin afectar su rendimiento. Esto los hace obvios candidatos para la alimentación y carga de dispositivos portátiles y situados lugares de difícil acceso. A pesar de ello, su uso no está muy extendido debido a que su relación eficiencia-coste es baja en comparación a otros métodos capaces de suplir las funciones de alimentación – como la sustitución periódica de baterías – o de conversión térmica-eléctrica – como las turbinas de vapor. Los materiales termoeléctricos suelen ser o eficientes y caros (como el Bi2Te3 usado en los módulos comerciales) o ineficientes y de bajo coste (como el silicio, barato por su abundancia ya que supone un 28% de la corteza terrestre). En este trabajo se han crecido nanostructuras de silicio y silicio-germano, con dimensiones en el orden de los 100 nm. Los nanomateriales presentan propiedades termoeléctricas mejoradas respecto a sus contrapartes macroscópicas. Gracias a la nanoestructuración pues, se ha abordado del problema de eficiencia-coste por dos vertientes: • En el caso del silicio – normalmente un mal termoeléctrico debido a su alta conductividad térmica – se ha habilitado su uso como termoeléctrico al crecerlo en forma de nanohilos cristalinos y nanotubos de silicio policristalino. • En el caso de silicio-germano – que ya es un buen termoeléctrico para uso en altas temperaturas – se ha aumentado su eficiencia aún más, creciéndolo en forma de nanohilos. Yendo más allá de la síntesis, los nanohilos de silicio/silicio-germano se han optimizado, caracterizado en integrado en gran número micro-generadores termoeléctricos de 1 mm2 de superficie, pensados para la alimentación de pequeños dispositivos y circuitos integrados. Respecto a los nanotubos de Si, estos se han obtenido en densas fibras macroscópicas aptas para su aplicación directa como generadores termoeléctricos de gran área. Cabe mencionar que ambos nanomateriales – así como los microgeneradores basados en nanohilos – fueron obtenidos mediante técnicas actualmente utilizadas para la fabricación de circuitos integrados, pensando en la escalabilidad del proceso para su aplicación. El trabajo presentado en esta tesis consiste en el crecimiento, optimización, estudio e integración de nanostructuras de Si/Si-Ge para su aplicación en generación termoeléctrica. En los Capítulos 1 y 2 se pone un marco a los materiales tratados y su aplicación y se describen los métodos utilizados, respectivamente. Los resultados se han dividido en cuatro capítulos. En los Capítulos 3, 4 y 5 se tratan los nanohilos abordando su crecimiento, caracterización y aplicación en microgeneradores, respectivamente. En el Capítulo 6 se tratan las fibras de nanotubos, integrando todo el estudio en el mismo capítulo. Finalmente en el Capítulo 7 se muestran las conclusiones, resumiendo los resultados e indicando la relevancia del trabajo.

Over the last decades of research on sustainable energy, thermoelectric generation has been identified as a potential energy harvesting solution for a wide range of applications. Nowadays, the commercial thermoelectric technology is almost entirely based on tellurium alloys, it mainly addresses room temperature applications and it is not compatible with MEMS and CMOS processing. In this work, silicon-germanium based micro-devices have been designed, developed and characterized with the aim of addressing the heat recovery needs of the automotive industry. The micro-scale of the fabricated devices, together with the full compatibility with silicon micro-processing, also profiles an interesting potential for application in the autonomous sensor field. Most importantly, the configuration and the fabrication processes of such silicon-based generators constitute a platform to transfer the results of decades of promising material investigations and engineering into practical micro-scaled thermoelectric generators. The room temperature characterization of the manufactured micro-generators revealed power factors up to 13.9x10-3 μW/(cm2K2) and maximum output power density up to 24.7 μW/cm2. In such temperature range, the micro-devices manufactured in this work are still not as performing as the state-of-the-art bismuth-telluride based technology. However, at around 300 C, the developed micro-modules are predicted to produce a maximum power output of 1.2-1.5mW under 10 C temperature gradient, which corresponds to 35-45% of the room temperature performance of the only commercial bismuth telluride based micro-devices. The results show that silicon-germanium micro-modules could potentially compete with the state-of-the-art commercial micro-devices, being better performing at higher temperature, but also offering the advantage of being a sustainable MEMS and CMOS compatible option for autonomous sensors integration.

Computers and their constituent electronics continue to shrink. The same amount of work can be done with increasingly smaller and cheaper components that need less power to function than before. In wireless sensor networks, the energy needed by one sensor node borders the amount that is already present in its immediate surroundings. Equipping the electronics with a micro generator or energy harvester gives the possibility that it can become self-sufficient in energy. In this thesis two kinds of energy harvesters are investigated. One absorbs vibrations and converts them into electricity by means of piezo-electricity. The other converts heat flow through a semiconductor to electricity, utilizing a thermoelectric effect. Principles governing the performance, actual performance of off-the-shelf components and design considerations of the energy harvester have been treated. The thermoelectric micro generator has been measured to output power at 2.7 mW and 20°C with a load of 10 W. The piezoelectric micro generator has been measured to output power at 2.3 mW at 56.1 Hz, with a mechanical trim weight and a load of 565 W. In these conditions the power density of the generators lies between 2-3 W/m2.

High heat fluxes generated by modern electronic chips continue to motivate efforts to improve the efficiency of associated cooling systems. This thesis seeks to enhance heat transfer in liquid-based micro-channel heat sinks, while keeping power consumption low, using geometrical modifications and the replacement of water coolant by nanofluids. Preliminary investigation of a perforated pinned heat sink shows that geometrical enhancement strategies proven for air-cooled systems do not necessarily work well with liquid coolant. However, simple solid cylindrical or prismatic vortex generators (VGs) positioned at intervals along the base of a micro-channel are found to offer heat transfer benefits for liquid coolants flowing under laminar conditions. The performance of various VGs with different cross-sectional shapes (including semi-circular, triangular, elliptical and rectangular) is examined using detailed finite element analysis validated against published experimental data. Results show that the half-circle VGs offer the best heat transfer improvement among the considered shapes, but with a substantial increase in pressure drop along the micro-channel. To reduce the pressure penalty, various gaps are introduced along the span of the VGs and shown to reduce the pressure while further improving the heat transfer performance. A performance evaluation criteria (PEC) index is used to assess the VG benefits versus pressure penalty. A critical evaluation of various (Al2O3/SiO2-water) nanofluids in terms of energy management is conducted, highlighting that performance comparisons at equal Reynolds numbers are misleading because of kinematic viscosity differences. Enhancement of heat transfer can appear much more significant than when comparing at equal flow rate. However, it is also shown that a novel combination of elliptical VGs with nanofluids can offer genuine benefits. Finally, an optimisation study illustrates that CFD-validated surrogate modelling provides an accurate representation of the system performance over a range of design parameters, enabling optimal heat transfer and pressure drop to be determined.

Smart sensors have become and will continue to constitute an enabling technology to wirelessly connect platforms and systems and enable improved and autonomous performance. Automobiles have about two hundred sensors. Airplanes have about eight thousand sensors. With technology advancements in autonomous vehicles or fly-by-wireless, the numbers of these sensors is expected to increase significantly. The need to conserve water and energy has led to the development of advanced metering infrastructure (AMI) as a concept to support smart energy and water grid systems that would respond to emergency shut-offs or electric blackouts. Through the Internet of things (IoT) smart sensors and other network devices will be connected to enable exchange and control procedure toward reducing the operational cost and improving the efficiency of residential and commercial buildings in terms of their function or energy and water use. Powering these smart sensors with batteries or wires poses great challenges in terms of replacing the batteries and connecting the wires especially in remote and difficult-to-reach locations. Harvesting free ambient energy provides a solution to develop self-powered smart sensors that can support different platforms and systems and integrate their functionality. In this dissertation, we develop and experimentally assess the performance of harvesters that draw their energy from air or water flows. These harvesters include centimeter-scale micro wind turbines, piezo aeroelastic harvesters, and micro hydro generators. The performance of these different harvesters is determined by their capability to support wireless sensing and transmission, the level of generated power, and power density. We also develop and demonstrate the capability of multifunctional systems that can harvest energy to replenish a battery and use the harvested energy to sense speed, flow rate or temperature, and to transmit the data wirelessly to a remote location.
PHD

This thesis provides a compendium for the use of microcontact printing in fabricating electrical devices. Work has been undertaken to examine the use of soft lithographic techniques for employment in electronic manufacture. This thesis focusses on the use of high electric field generators as a means to producing electroluminescent devices. These devices provide a quantifiable output in the form of light. Analysis of the electrical performance of electrode structures can be determined by their success at producing light. A prospective reduction in driving voltage would deem these devices more efficient, longer lasting and an improvement on current specification. The work focussed on the viability of using relatively crude print techniques to create high resolution structures. This was carried out successfully and demonstrated that lighting structures of 75 μm and 25 μm have been produced. Microcontact printing has been established as a method for patterning gold surfaces with a functionalising self-assembled monolayer using alkanethiol molecules. This layer is then utilised as an etch resist layer to expose gold tracks for use as electric field generator electrode arrays. Through careful analysis of each step of the printing process, techniques were developed and reported to create a robust and repeatable print mechanism for reliability and accuracy. These techniques were employed to optimise the print process culminating in the development of each stage and final electrode structures mounted on a rigid backplate for use as electroluminescent devices for characterisation. These devices were then modelled for their electrical characteristics and investigated for being used in low voltage application. In this case for the development of electroluminescent applications, a driving voltage of 65 V was achieved and represents a significant advance to the field of printed electronics and Electroluminescence.

L’essor considérable des applications liées aux récents progrès de l’internet des objets (IoT) nécessite de développer de nouvelles solutions de collecte de l’énergie environnante pour alimenter les microsystèmes. L’abondance de la chaleur dans notre environnement permet aux dispositifs de récupération de l’énergie thermique d’être une des solutions. Dans ce travail, nous avons développé une famille de micro-générateurs thermoélectriques planaires (µTEG), intégrant une topologie originale de thermopile en 2.5D périodiquement repliée et distribuée sur multi-membrane, capable de convertir de manière directe la chaleur en énergie électrique utile. Cette thermopile, à grande densité d’intégration, emploie des thermocouples à base de matériaux thermoélectriques métalliques (Chromel et Constantan), associés électriquement soit en série, soit en parallèle, permettant de réduire drastiquement la résistance électrique interne de ces µTEGs, à quelques dizaines de Ohms. Pour obtenir de ces modules une puissance de sortie maximale, des modélisations numériques 3D sous COMSOL Multiphysics®, au niveau thermique, ont permis d’optimiser leur dimensionnement. La fabrication de ces dispositifs a été réalisée par des procédés compatibles CMOS, à faible coût, utilisant des matériaux non polluants, abondants, et respectueux de l’environnement. Elle a employé la technique de gravure profonde DRIE de wafers de Silicium pour libérer des membranes de longueurs ajustables permettant d’adapter la résistance thermique des µTEGs à leur environnement. Les dispositifs réalisés en centrale de technologie ont été caractérisés à l’aide de bancs de mesure spécifiques développés à cette fin. La récupération d’un Watt de chaleur permet d’atteindre des puissances électriques thermogénérées de quelques centaines de microwatts. Cela classe ces nouveaux µTEG 2.5D parmi les meilleurs µ-modules de l’état de l’art utilisant des thermoélectriques métalliques
The tremendous growth of applications related to recent advances in the Internet of Things (IoT) requires the development of new solutions for harvesting/scavenging the environmental energy to power microsystems. The abundance of heat in our environment allows thermal energy harvesting devices to be one of the solutions. In this work, we have developed a family of planar micro-thermoelectric generators (µTEG), integrating a novel 2.5D thermopile topology periodically folded and distributed on multi-membrane, capable of converting heat directly into useful electrical energy. This thermopile, with high integration density, uses thermocouples based on metallic thermoelectric materials (Chromel and Constantan), electrically associated either in series or in parallel, allowing to reduce drastically the internal electrical resistance of these µTEGs to a few tens of Ohms. A 3D thermal modelling in COMSOL Multiphysics® was used to design the optimal dimensions of the modules so they would deliver the maximum output power. The fabrication of these devices is made by low-cost CMOS-compatible processes, using non-polluting, abundant and environmentally friendly materials. Deep reactive ionic etching (DRIE) of Silicon wafers is used to release membranes with adjustable lengths allowing to adapt the thermal resistance of these µTEGs to their environment. The devices realized in IEMN clean room, have been characterized using specific measurement benches developed for this purpose. The harvesting of one Watt of heat leads to thermo-generated electrical powers of a few hundred microwatts. This ranks these new 2.5D µTEGs among the best state-of-the-art µ-modules using metallic thermoelectrics

L'internet des objets (Internet of Thing, IoT) suscite de plus en plus d'attention dans l'industrie électronique. L'IoT est un concept selon lequel les objets de tous les jours pourront communiquer ensemble via Internet. La plupart des objets connectés utilisent des batteries qu’il faut changer régulièrement ou recharger. Face à la forte croissance annoncée, la recherche de sources d’alimentation autonomes et alternatives s’appuyant sur des systèmes qui capturent l’énergie ambiante et la convertissent en électricité devient primordiale. Parmi les technologies de récupération d’énergie, la thermoélectricité présente des avantages certains liés à sa simplicité, sa fiabilité et son absence de pièces mobiles et de pollution par émission de gaz à effet de serre. L’ensemble de ces caractéristiques favorables place les convertisseurs thermoélectriques comme des candidats possibles pour fournir aux objets connectés de demain les faibles quantités d’énergie nécessaire à leur fonctionnement ou pour recharger les batteries. Mes travaux de thèse s’inscrivent dans ce contexte et se sont déroulés en partie dans le cadre du projet Européen EnSO (Energy for Smart Objects). Des études numériques menées avec le logiciel commercial Comsol Multiphysics ont été réalisées sur des micro-générateurs planaires innovants développés par la société Mahle, partenaire du projet. L’objectif de ces travaux était de comprendre l’influence de nombreux paramètres (géométrie, conditions aux limites en terme de température ou de flux, propriétés électrique et thermique des matériaux actifs) sur leurs performances thermoélectriques (puissance électrique et rendement). Nous avons montré, en particulier, le rôle critique des résistances de contact électriques et thermiques sur la puissance électrique de sortie. Un second volet, plus expérimental, a été consacré au développement de générateurs thermoélectriques miniatures à forte densité de puissance intégrant des matériaux avancés à base de skutterudites. Plusieurs brasures ont été testées lors de l’assemblage des modules thermoélectriques. La caractérisation des performances des modules (25-500°C) couplée aux calculs numériques ont permis de guider les recherches et d’optimiser les procédés de fabrication. Ce travail a abouti à l’obtention d’une densité de puissance record (3,3 W/cm2 pour une différence de température de 450 K) par rapport à l’état de l’art
The Internet of Thing (IoT) is currently being intensively explored in the electronic industry. IoT is an extension of Internet connectivity into physical end everyday-life objects which will be able to communicate and interact with each other’s. Most of these connected objects are powered by batteries that need to be regularly switched or recharged. Faced with a strong announced growth of their number in coming years, the search for novel alternative, autonomous power supplies that convert surrounding available energy into electricity becomes essential. Among energy harvesting technologies, thermoelectricity is advantageous due to its simplicity, reliability, the absence of moving parts and greenhouse gas emissions. All these favorable characteristics make thermoelectric converters possible candidates for powering or recharging batteries of connected objects. In this context, my PhD work was done within the frame of the European project EnSO («Energy for Smart Objects»). Numerical studies with the software Comsol Multiphysics were performed on innovative planar micro-generators developed by the Mahle company, one of the partners of this project. The main objective of this work was to achieve a better understanding of the influence of numerous parameters (geometry, boundary conditions in terms of temperature and flux, electrical and thermal properties of the active materials) on their thermoelectric performances (output power and efficiency). In particular, we have underlined the critical role played by the electrical and thermal contact resistances on the output power. A second part of this study has been devoted to the experimental development of miniaturized thermoelectric generators capable of delivering high output power density through the integration of skutterudite materials. Several brazes have been tested during the assembly operations of the thermoelectric modules. The characterization of the module performances (25-500°C) combined with numerical calculations have been used as a guidance for optimizing the fabrication process. This work culminated in the successful fabrication of a thermoelectric module with a record-breaking power density of 3,3 W/cm2 achieved under a temperature difference of 450 K

A recente abertura de mercado, a carência de recursos públicos para investimentos em geração de energia, a dificuldade de realização de empreendimentos de grande porte por razão ambiental, bem como o programa de universalização do atendimento têm criado novas oportunidades no Setor Elétrico brasileiro, dentre as quais está a exploração de geração distribuída. Nesse âmbito, as micro redes que associam vários geradores de pequeno porte, operados por centro regional, vêm se revelando como uma interessante solução tanto para o investidor como para o atendimento de áreas de concessão específicas. Esta pesquisa apresenta um modelo de análise econômica da participação de geradores distribuídos, operando de forma pseudo-cooperativa, fundamentado na teoria dos jogos. O modelo foca o cliente, com futuro potencial de ser livre, capaz de gerar a sua própria energia através de geradores distribuídos. Uma micro-rede de geradores distribuídos pode ser constituída de vários agentes que, não obstante tenham toda ou parte de sua produção contratualmente comprometida, resolvem atuar de forma cooperada para auferir o ganho decorrente dos diferentes custos marginais de operação das máquinas, para cada nível de despacho de suas unidades. O modelo proposto prevê que a otimização da participação dos despachos das unidades cooperadas, em cada situação de carga, é obtida pela minimização global dos custos marginais totais, determinando a produção de cada gerador. O compartilhamento doganho advindo da cooperação é dado pela aplicação da Função de Shapley, que se fundamenta nas características técnicas e econômicas de operação de cada unidade. ) O modelo desenvolvido neste trabalho formulou o conceito pseudo-cooperação, que prevê a disponibilidade parcial da capacidade de geração de um ou mais agentes para produção dedicada à demanda cooperada da micro rede, de forma que a capacidade restante permanece para o agente oferecer a oportunidades do mercado. A otimização dos ganhos, tanto da rede cooperada como do agente que disponibiliza parte de sua capacidade ao mercado, é realizada através do compartilhamento do ganho da cooperação, da receita obtida da venda de energia ao mercado e do prêmio que o(s) agente(s) que transgride(m) sua(s) cota(s) mínima(s) de cooperação paga(m) aos participantes da cooperação. Com essa abordagem de cooperação parcial e otimização dos ganhos tornou-se possível maximizar os benefícios para os agentes e obter uma capacidade adicional, chamada neste trabalho de \"Sobra\", disponível para venda ao mercado. Desta forma, e como conclusão principal, pôde-se verificar que é possível a obtenção de ganhos adicionais sempre que um ou mais geradores trabalham de forma cooperada e que a pseudo-cooperação apresenta uma forma de aumentar esse ganho
The recent market expansion, the lack of public resources for investments in power generation, the difficulty of deployment of large projects due to environmental reasons, and also the program \"Universalização do Atendimento\" (program that aims to attend all country) has provided new opportunities on the Brazilian Electric Sector. One of these opportunities is the exploration of distributed generation. Under this idea, an interesting solution for the investor and also for the service provider in specific concession areas is the micro-grids. The micro-grids associate several small load generators it selves and these micro-grids are operated by regional centers. This research presents a model of economical analysis of the participation of distributed generators, operating in a pseudo-cooperative way, based in the game theory. The model adresses non free consumers that further may have the capability to be able to generate its own energy through distributed generators, as free consumers. A micro-grid of distributed generators can be composed by several agents that decide to act in a cooperative way aiming to earn from each level of dispatched power, through the different operational cost of the machines in the micro-grid. This is possible even having all or part the production already contractually committed. For each load situation, the proposed model foresees that the dispatch of power in each cooperated units is optimized by the global reduction of the costs thataffect the production of each generator. The share of the gain from the cooperation is given by the application of the Shapley function that is based in the technical and economical characteristics of operation of each unit. ) The developed model in this work has formulated a pseudo-cooperation concept, which foresees the partial availability of the generation capacity of one or more agents for dedicated production to the cooperated demand of the micro grid, so that the remaining capacity is available to be offered to opportunities of the market. The optimization of the gain over the cooperated grid, and also over the agent that make available its partial capacity to the market, is accomplished through the share of the cooperated gain, through the revenue obtained from the energy sold to the market, and also through the prize that the agents pay to other participants of the cooperation when they reach their minimal commitment. With the partial cooperation and gain optimization approach, it was possible to maximize the benefits for the agents and to obtain a surplus, called in this work of \"Sobra\", available to sell to the market. The main conclusion is that it is possible to obtain additional benefits whenever one or more generator work in a cooperative basis and that the pseudo-cooperation is a way to grown this benefits.

L'intégration des sources d'énergies renouvelables sur le réseau électrique est complexe en raison de leur nature intermittente et décentralisée. Le micro-réseau est une approche prometteuse pour interconnecter des générateurs distribués (DGs) locaux, alimenter des charges locales et également échanger de l'énergie avec le réseau électrique de manière contrôlée. Ce mode de production/consommation locales permet d'éviter la transmission d'électricité sur de longues distances, et implique donc une plus grande efficacité. Ces travaux se concentrent sur l'analyse et le contrôle du micro-réseau continu afin que les DGs se répartissent l'alimentation des charges et qu'ils maintiennent également la tension du bus continu. À l'équilibre, les contraintesde la commande du statisme classique (droop control) pour un système comportant de multiples DGs sont analysés, et une méthode de compensation mixte est proposée pour améliorer simultanément le maintien en tension et le partage du courant de charge. En dynamique, le modèle global du système est construit en introduisant une inductance virtuelle dans le circuit équivalent du DG, puis plusieurs modèles d'ordre réduit sont examinés pour vérifier leur efficacité dans l'analyse de la stabilité du système. Un modèle multi-échelle d'ordre réduit (RMM) est proposé afin de conserver les contraintes temporelles ainsi que de réduire la complexité du système. Enfin, une méthode basée sur le contrôle de rejet de perturbation active (ADRC) est présentée afin de mettre en oeuvre le contrôle local de la tension des DG en prenant en compte l'échelle de temps. Cette méthode permet d'améliorer la dynamique du système de contrôle en ajustant la largeur de bande passante de la commande et de l'observateur. Les analyses et les méthodes de contrôle proposées sont vérifiées par des essais expérimentaux dans notre plateforme au laboratoire
The direct integration of renewable energy resources to the utility grid is pretty tough due to their intermittent feature and dispersed nature. Microgrid is one promising approach to gather the local distributed generators (DGs), supply local loads as well as exchange power with the utility grid as a controllable unit. This local-generation-localconsumption mode is able to avoid the long distance power transmission, thus can benefit a higher efficiency. The control aim of DC microgrids is to make the multiple DGs share the load properly as well as maintain the DCbus voltage stable. In steady state, the constrains of the classic droop control in multiple DGs environment are analyzed, and a mixed compensation method using common current is proposed to improve the voltage and load sharing performance simultaneously. In dynamic state, the system comprehensive model is constructed by the introduction of virtual inductor in the equivalent circuit of the DG, then several reduced-order models are examined to check their effectiveness for the system stability analysis. A reduced-order multi-scale model (RMM) is proposedto keep major time scale information as well as reduce the system complexity. Finally, an active disturbance rejection control (ADRC) based control method is proposed to realize the time scale droop control. It can effectively adjust the dynamic of the local control by adjusting the bandwidth of the Linear Extend State Observer or/and the controller. The proposed analysis and control methods are verified by experimental tests in our laboratory platform

Small wind turbines, and especially urban-mounted turbines which require no dedicated pole, have garnered great public enthusiasm in recent years. This enthusiasm has fueled widespread growth among energy conservationists, and estimates predict that the power produced nationally by small wind will increase thirty-fold by 2013. Unfortunately, most of the wind resources currently available have been designed for larger, rural-mounted turbines; thus, they are not well suited for this nascent market. A consequence of this is that many potential urban small wind turbine owners over-predict their local wind resource, which is both costly and inefficient. According to a recent study published by Encraft Ltd., small wind turbines mounted to buildings far underperformed their rural pole mounted counterparts. As a proposed solution to this problem, this project introduces the concept of a Web-based Wind Assessment System (WWAS). This system combines all the necessary resources for potential urban small wind turbine customers into a single web-based tool. The system also presents the concept of a modular wind measurement system, which couples with the WWAS to provide real-time wind data measurements. The benefits of the system include its ease of use, flexibility of installation, data accessibility from any web browser, and expert advice. The WWAS prevents potential clients from investing in a system that may not be viable for their location. In addition, a small wind turbine is designed in this project, which has a unique modular mounting system, allowing the same baseline wind turbine to attach to various structures using interchangeable mounting hardware. This includes such accessible urban structures as street lights, building corners, flag poles, and building walls, among others. This design also utilizes concepts that address some of the challenges associated with mounting small wind turbines to existing urban structures. These concepts include: swept tip blades and lower RPM to reduce noise; vibration suppression using rubber shims; a netted duct to protect wildlife; and a direct-drive permanent magnet generator to ensure low starting torque. Finally, the cost of this system is calculated using off-the-shelf components, which minimize testing and certification expense. This small wind turbine system is designed to be grid-connected, has a 6 foot diameter rotor, and is rated at 1 kW. This design features a unique modular interchangeable mounting system. The cost for this complete system is estimated to be $2,050. If a users' site has an average wind speed of 14 mph (6.5 m/s), this system will generate a return on investment in 8.5 years, leaving over 10 years of profit. The profit for this system, at this sample average wind speed, yields over $4,000 during its 20-year design life, which is a two-fold return on investment. This project has implications for various stakeholders in the small wind turbine market, including designers, engineers, manufacturers, and potential customers. Equally important is its potential role in guiding our future national--even global--energy agenda.

The taming of electricity and its widespread use allows people to see in the dark, to speak to one another instantaneously across the earth, and it allows retrieval of data from instruments sent out of the solar system. It is right to expect that the uses and demand for electricity will continue to grow, and to extend the ability to generate electricity; here two new micromachined devices for converting mechanical energy into electrical energy are presented. Aided by the wealth of micromachining process technology, generators that use an oscillatory motion to modify the physical structure of a capacitor with a built-in electric field provided by a permanent electret have been designed, built, and tested. The electret creates an electric field inside the capacitor structure, which induces mirror charge at some potential. The modification of the capacitor then generates an alternating displacement current through an external circuit, which provides useful electrical power. The electret microphone is a similar well known device for converting pressure waves into electrical signals by varying the distance between two charged capacitive plates. This work explores and proves feasible the ability to use mechanical forces to change the overlapping area of a charged capacitor structure and using mechanical forces to move a liquid into the gap of a charged capacitor structure, changing its permittivity to produce electricity. This work demonstrates 2.5mW of power from a 2cm diameter rotary generator at 12kRPM and 10[micro]w for a 0.1cm3 linear shaking generator at 60Hz.

Energy harvesting from the surrounding environment has become a hot topic in research as an alternative powering solution. The concept deals with scavenging, as well as, harvesting energy from the surrounding energy sources. Harvesting vibrations, through Micro-Power Generators (MPGs) , has drawn a lot of attention recently due to the reduction in the power requirement of the current sensors and integrated ciruits, and the abundance of ambient vibrations in many environments. Vibration Micro-Power generators (VMPGs) use one of three transduction mechanisms: piezoelectric, electromagnetic or electrostatic. Although electrostatic MPGs are the most compatible mechanism with ICs technology, many challenges face their optimal operation including low efficiency due to power electronics switching losses, the need for pre-charge, and the inability to operate in vibration environments with low frequencies and amplitudes. The objective of this thesis is to develop novel electrostatic micro-power generators using switchless architecture to achieve low cost, small footprint, self-sustained and optimal power generation in different vibration environments including low frequencies and amplitudes. The first electrostatic MPG uses an out-of-plane capacitive transducer. The new generator is sensitive enough to extract output power at very low base excitations. It is designed to use ready-made electret as a charging source and is therefore portable and self-sustained. Moreover, the new MPG can be configured as a wideband MPG in its impact mode of operation. A bandwidth of up to 9 Hz has been realized in this mode of operation. An improved version of the MPG is also presented that produces almost 1mW output power at a base excitation amplitude and frequency of 0.08g (RMS) and 86 Hz. Two nonlinear models developed for the free-flight and impact modes of operation of the MPG are presented to allow future analysis and optimization of the system. The second electrostatic MPG uses a novel interdigitated in-plane parallel plate electrostatic transducer. The new implementation can achieve 78% more output power than the original cited implementation. The MPG is fabricated using MEMS surface micromachining. The MPG introduces a new beam suspension system in which the source voltage is unlimited by the pull-in instability and low MPG center frequency can be realized. The MPG uses charged silicon nitride as a charging source. The MPG produces 65 mV at a base acceleration amplitude and frequency of 2g and 1.1 kHz. The prototype achieves 27% less resonance frequency with only one eight the size of the previous implementation. A third electrostatic MPG architecture is introduced. The new architecture eliminates the need for restoring force elements (springs) in the MPG. The architecture can realize arbitrarily low MPG center frequency. It is suitable for both rectilinear and cylindrical structures and can be used with different vibration energy transduction methods. A prototype is fabricated and tested to demonstrate the feasibility of this architecture. The center frequency of the prototype is found to be 2 Hz demonstrating low frequency operation. The nonlinear behavior of switchless (continuous) electrostatic MPGs is further studied for optimal power operation. A consistent approximate analytical solution is developed to describe the nonlinear behavior of switchless comb-finger electrostatic MPGs. The method of multiple scales is used to develop such model. The model was found to be valid for MPGs operating under tight electromechanical coupling conditions and for moderately-large base excitations.

Energy harvesters collect and convert energy available in the environment into useful electrical power to satisfy the power requirements of autonomous systems. Vibration energy is a prevalent source of waste energy in industrial and built environments. Vibration-based energy harvesters, or vibration-based micro power generators (VBMPGs), utilize a transducer, a mechanical oscillator in this application, to capture kinetic energy from environmental vibrations and to convert it into electrical energy using electromagnetic, electrostatic, or piezoelectric transduction mechanisms. A key design feature of all VBMPGs, regardless of their transduction mechanism, is that they are optimally tuned to harvest vibration energy within a narrow frequency band in the neighborhood of the natural frequency of the oscillator. Outside this band, the output power is too low to be conditioned and utilized. This limitation is exacerbated by the fact that VBMPGs are also designed to have high quality factors to minimize energy dissipation, further narrowing the optimal operating frequency band. Vibrations in most environments, however, are random and wideband. As a result, VBMPGs can harvest energy only for a relatively limited period of time, which imposes excessive constraints on their usability. A new architecture for wideband VBMPGs is the main contribution of this thesis. The new design is general in the sense that it can be applied to any of the three transduction mechanisms listed above. The linear oscillator is replaced with a piecewise-linear oscillator as the energy-harvesting element of the VBMPG. The new architecture has been found to increase the bandwidth of the VBMPG during a frequency up-sweep, while maintaining the same bandwidth in a frequency downsweep. Experimental results show that using the new architecture results in a 313% increase in the width of the bandwidth compared to that produced by traditional architecture. Simulations show that under random-frequency excitations, the new architecture collects more energy than traditional architecture. In addition, the knowledge acquired has been used to build a wideband electromagnetic VBMPG using MicroElectroMechanical Systems, MEMS, technology. This research indicates that a variety of piecewise-linear oscillators, including impact oscillators, can be implemented on MPG structures that have been built using MEMS technology. When the scale of the MPGs is reduced, lower losses are likely during contact between the moving oscillators and the stopper, which will lead to an increase in bandwidth and hence in the amount of energy collected. Finally, a design procedure has been developed for optimizing such wideband MPGs. This research showed that wideband MPGs require two design optimization steps in addition to the traditional technique, which is used in all types of generators, of minimizing mechanical energy losses through structural design and material selection. The first step for both regular and wideband MPGs minimizes the MPG damping ratio by increasing the mass and stiffness of the MPG by a common factor until the effect of size causes the rate at which energy losses increase to accelerate beyond that common factor. The second step, which is specific to wideband MPGs, tailors the output power and bandwidth to fit the Probability Density Function, PDF, of environmental vibrations. A figure of merit FoM was devised to quantify the quality of this fit. Experimental results show that with this procedure, the bandwidth at half-power level increases to more than 600% of the original VBMPG bandwidth.

Thesis advisor: Christopher Maxwell
Criminal hotspots are heuristically understood, but seldom well-defined and empirically evaluated. In this thesis, I examine the concentration of crime into microgeographic hotspots, testing both the extent to which this occurs across major cities and the relationship between spatial features and crime. I find that roughly five percent of street segments are responsible for half of crime across major cities, with this concentration level being robust to changes in total crime rate and economic conditions over time. I also find a significant relationship between the presence of spatial features such as nearby schools, bus stops, bars, and graffiti with the crime level in microgeographic units. Through a routine activity and crime pattern theoretic interpretation, such spatial models of crime can help to identify features and facilities that attract, inspire, and deter crime. These findings have policy relevant implications for both urban planning and police strategy, offering intuition as to where crime can be expected to concentrate and how changes to local environments impact public safety
Thesis (BA) — Boston College, 2017
Submitted to: Boston College. College of Arts and Sciences
Discipline: Departmental Honors
Discipline: Economics

碩士
國立中興大學
機械工程學系所
105
In this study, we present a thermoelectric microgenerator fabricated using the standard 0.18 μm CMOS (complementary metal oxide semiconductor) process are investigated. The thermoelectric microgenerator consists of 129 thermocouples in series, and the thermocouples are composed of p-type and n-type polysilicons. The output power of microgenerator relies on the temperature difference between the hot and cold parts of thermocouples. To increase the temperature difference of thermocouples, the hot part of thermocouples is designed as the suspended structure. Then, the hot part of the thermocouples is coated by CNCs (Carbon nanocapsules) that increasing absorb radiant heat source. The cold part of thermocouples is formed on the silicon substrate, and covered by silicon oxide that provides low thermal conductivity and thermal isolation. The FEM (finite element method) software of ANSYS Workbench is employed to simulate the temperature distribution and temperature difference of the thermoelectric microgenerator, and analyzed the optimal geometry of the thermocouples. The experimental results showed that the output voltage and output power of the microgenerator without CNCs film were 4.426 mV, and 224.65 pW, respectively, at the temperature difference of 3.6 K. The output voltage and output power of the microgenerator with CNCs film were 5.845 mV and 391.789 pW, respectively, at the temperature difference of 4.3 K. The microgenerator had the voltage factor of 0.882 mV/k/mm2 and the power factor of 13.686 pW/K2/mm2.

碩士
國立臺灣科技大學
電機工程系
96
With the rapid advancement of technology, the demand of all kinds of resources is increasing. Therefore, the issues about energy saving and environment protection are getting more and more attention. As a result,the micro power generator is receiving a considerable amount of interest as a means for energy saving. In this thesis,we brief introduction about power generator principle, type and application will be given first. A circuit of input rectifierless AC-to-DC converter system will be implemented to convert the low output voltage of micro power generator. Using two DC-to-DC converters rather than a bridge rectifier, the presented system can work for low input AC voltage sources. The mathematical model and circuit implementation will be presented in the context. In order to verify the correctness of the proposed systems, simulation and experimental results are also provided to validate the context.

碩士
國立臺北科技大學
機電整合研究所
96
This paper describes device design and manufacturing process to generate single microbubbles for biomedical applications. With MEMS technology several cross-shaped microchannels are designed and fabricated by using the SU-8 photoresist mould and Polydimethylsiloxance (PDMS) material. The microbubble generator controls gas and liquid inlets to segment continuous fluids, referred to as two-phase flow, in the microchannels. The void segments filled with gas thus form initial microbubbles. These microbubbles are then transferred to the next-stage microchannels for further bubble separation and size reduction. The ultimate diameter of microbubbles is expected to reach less than 50 μm. With further harden and collection processes the microbubbles are able to enhance imaging effect in ultrasound or MRI medical applications; besides, they can elevate delivery efficiency of drug or cosmetics, and more importantly, bio-effect of ultrasound gene therapy.

碩士
國立中興大學
機械工程學系所
101
This study presents a micro thermoelectric power generator fabricated by the standard 0.18 μm 1P6M (one polysilicon and six metals) CMOS (complementary metal oxide semiconductor) process. The micro thermoelectric power generator is composed of 370 thermocouples in series, and the thermocouples are formed by p-type and n-type polysilicon. The efficiency of the micro generator depends on the temperature difference between hot and cold parts of thermocouples. In order to achieve the best generation efficiency, the reactive ion etching (RIE) is used to release the hot part of thermocouples. Then, the hot part of the thermocouples is coated by MCNTs (Multi-walled carbon nanotubes). The cold part of the thermocouples is covered by silicon oxide that provides low thermal conductivity and thermal isolation. ANSYS Workbench is used to simulate the temperature distribution and the temperature gradient of the micro generator. The experimental results showed that the output voltage of thermoelectric generator without MCNTs film was 0.899 mV and the output power was 1.72 pW when temperature was 400 K. The output voltage and output power of the generator with MCNTs film were 1.56 mV and 5.16 pW, respectively, at the temperature of 400 K. The micro generator with the MCNTs film had a voltage factor of 0.225 mV/K/mm2 and a power factor of 0.745 pW/K2/mm2. Finally, the charging circuit is designed to carry out the storage of output power, and the power can be apply in the low power electronic component.

碩士
國立中興大學
機械工程學系所
99
In this study, we present a micro thermoelectric generator fabricated by the standard 0.18 μm 1P6M (one polysilicon six metal) CMOS (complementary metal oxide semiconductor) process. The micro thermoelectric generator is composed of 33 thermocouples in series, and the thermocouples are formed by p-type and n-type polysilicons. The dimensions of the thermocouples are 120 μm length and width 8 μm, which can generate the maximum output power. Micro thermoelectric generator efficiency depends on the temperature difference between hot and cold thermocouples. In order to prevent heat-receiving in the cold part of the thermocouples, the cold part is covered with a low thermal conductivity of silicon dioxide layer to insulate the heat source. The hot part of the thermocouples is suspended and connected to an aluminum plate, to increases the heat-receiving area. Coventor Ware and AMSYS are used to simulate temperature distribution of the suspended structure. The Simulated results show that the generator with suspended plate can increase the temperature difference of 0.64 K. The generator requires a post-CMOS process to release the suspended structures. The post-CMOS process uses an anisotropic dry etching to remove the oxide sacrificial layer and an isotropic dry etching to etch the silicon substrate. Experimental results show that the optimization efficiency of the generator is 0.551 % at the temperature difference of 5 K and 2.146 % at the temperature difference of 50 K. The experiments depict that the output voltage and output power of the micro generator are 0.185 mV and 1.07 μW, respectively, as the temperature difference is 5K. The voltage factor of the micro generator is 12.59 mV/K/cm2 and its power factor is 14.564 μW/K/cm2.

碩士
國立中山大學
機械與機電工程學系研究所
95
With the flourishing development of MEMS, it is possible to combine micro-sensors with micro-actuator and apply to the organ transplant in medical fields or as an embedded sensor on buildings or bridges. Generally batteries is are used as the kinetic energy source, but it involves the issue of recycling. Therefore, development of a self-generator utilizing vibrational source from environment is another better choice. This study succeeds in building up the transform mode of electricity in an electro-magnetic vibration-induced micro-generator. The electricity characteristics of micro-generator are obtained by Mathematical software analysis. MEMs technology can be used to fabricate and assemble the microstructure , planar coils and magnetic films. The analytic results of maximum power and minimum volume by using a mathematics model are achieved. The validity of this model is verified by comparing the theoretical and experiment data from the literature.

碩士
國立中央大學
電機工程學系
105
In this paper, the converter is used to simulate the synchronous generators. In island mode, converter can meet load requirements and provide stable voltage and frequency support .In grid-connected mode, converter can output request active power or reactive power. The control strategy of the virtual synchronous generators (VSG) is making distributed power supply operate safely and stably. The virtual synchronous generators are need to realize seamless transform between the island mode and grid-connected mode .This paper use a pre-synchronous method of VSG based on virtual power and secondary frequency and voltage regulation is put forward to achieve seamless transform. In island mode, multiple VSGs connected to work as a unit, each VSG should according to the capacity to sharing power which required by load . This paper simulates the operation of the virtual synchronous generator in Matlab/Simulink, and verifies the effectiveness of the proposed control algorithm.

碩士
國立成功大學
機械工程學系
103
When a liquid jet experiences axisymmetric disturbance, the disturbance grows in space, moves downstream, and eventually breaks up the jet into droplets. The phenomenon is called capillary instability, also known as Rayleigh breakup. Based on this instability, the present study develops droplet generators made of low temperature co-fired ceramics (LTCC). Both the monodisperse and multi-size droplet generators are successfully fabricated. The LTCC generator is driven by a piezoelectric disc attached directly on a LTCC diaphragm to provide the necessary disturbance. A backpressure is provided to the chamber of the generator such that a liquid jet can be formed steadily through a nozzle. Nozzles with different diameters are manufactured successfully by CO2 laser drilling. It is shown that the proportion of glass in the LTCC green tape and the parameters of laser drilling are key factors in fabricating the nozzle. Results show that the droplet sizes depend on excitation frequency, nozzle diameter and jet velocity. In the range of working frequency, the sizes of the droplets agree well with theoretical predictions.

博士
國立中山大學
機械與機電工程學系研究所
98
This work presents design and fabrication technologies on vibration-induced electromagnetic micro-generators using LTCC (Low temperature co-fire ceramic) processes. LTCC fabrication with some special advantages has simplistically processes and multilayer stack procedure, resulting in a micro-inducer can consist of the multilayer silver (Ag) induction micro-coils and a helical ceramic micro-spring. Highly electrical conductible Ag and its multilayer micro-coil structures can enhance the power output of generators. This work is composed of three parts. The first part describes the design of two kinds of micro-generator; a magnetic core generator (MCG) and sided-magnet generator (SMG). According to their respective structures, an analytical mode is also developed to investigate its resonant frequency and the spring constant of the micro-spring, as well as the bending stress and fatigue life of the supporting beam. The voltage output, current output and power output on the helical induction micro-coils, as well as the relationship of vibration amplitude versus vibration frequency in the vibrating system are calculated. The second part introduces how to integrate the Ag multilayer induction micro-coils and the helical ceramic micro-spring using LTCC technique, and organize the design and fabrication of LTCC micro-inducers. From the fabrication procedures, it is known that a stacking error places a limit on the total numbers of micro-coils layer. The experimental results verify that the application of LTCC to the fabrication of micro-inducers is feasible, and that the phenomenon of plane warpage, volumetric shrinkage, layer delamination and surface crack of sintered ceramic structures has been fully controlled. In the third part, measurement setup, vibrating tests and experiments on generating electricity are completed. The performances with different-structure devices are evaluated. Voltage output, current output and power output, as well as changing trends of power density with respect to the layer number of induction micro-coils and magnets are discussed. Relationship of the electrical parasitical damping coefficient versus the vibration amplitude and vibration velocity, relationship between the induced inductor and the current output, the power output depending on the electrical load resistance and differences between fabrication lots are investigated. At last, comparisons between analytical and experimental power output are conduced. For MCG micro-generator, the analytical value is 0.88 mW, about 13.6% smaller than the experimental value of 1 mW. For SMG micro-generator, the analytical value is 1.73 mW, about 10.7% larger than the measured value of 1.56 mW. The analytical models are verified. In the MCG device, the experimental results show that a maximum voltage output of 25.19 mV, a current output of 82.9 mA and a power density of 2.36 mW/cm3 under 120 Hz frequency and 0.03-mm amplitude are obtained. In addition, when operated at 69 Hz vibration frequency and vibration amplitude of 0.03 mm, the experimental maximum voltage output, current output and power density of the SMG device are 44.5 mV, 83.1 mA and 2.17 mW/cm3, respectively. Except the power density, other electricity performances of SMG device are better than MCG. Apparently, the power density of MCG and SMG device presented by this study competes favorably with the results from other devices in the literature.

碩士
國立臺灣科技大學
電機工程系
97
Climate change and the need to manage diminishing fossil fuel reserves are two of the biggest challenges the modern world faces today. In order to secure the future for ourselves and generations to follow, people must act now to reduce energy consumption and substantially cut greenhouse gases, such as carbon dioxide. Energy efficiency and renewable energy are parts of the answer, not only to climate change, but securing future energy resources as well. Among many types of renewable energies, micro power generators (MPGs) which harvest energy from ubiquitous environmental excitation have gained immense attention in the last decade. In this thesis, surveys about power generation principle, type, and applications of MPGs will be given first. Due to the low output voltage and low output power characteristics of MPG, special requirement of circuit design should be addressed. MPGs typically generate AC voltage while the load often requires DC voltage. Therefore, an AC-to-DC converter is required. In this thesis, input rectifierless converter is chosen as the power converter and a microcontroller is then used to implement the controller of the presented converter. In this thesis, digital PID compensator and digital filter are utilized as the digital controller. This thesis proposes a portable biomedical sensor using micro-generator as power supply. The proposed sensor system consists of a Zigbee wireless module to achieve the goal of remote supervision. Detailed design and implementation will be presented in the context. In order to verify the correctness of the proposed systems, simulation and experimental results are also provided to validate the context.

Many of the most pressing global challenges today and in the future center around the scarcity of sustainable energy and water sources. The innovative microbial fuel cell (MFC) technology addresses both as it utilizes bacteria to convert wastewaters into electricity. Advancing this technology requires a better understanding of the optimal materials, designs and conditions involved. The micro-sized MFC was recently developed to serve this need by providing a rapid testing device requiring only a fraction of the materials. Further, development of micro-liter scale MFCs has expanded into potential applications such as remote and self-sustained power sources as well as on-chip energy generators. By using microfabrication, the fabrication and assembly of microsized MFCs is potentially inexpensive and mass produced. The objective of the work within this dissertation was to explore and optimize the micro-sized MFC to maximize power and current generation towards the goal of a usable and application-oriented device. Micro-sized MFCs were examined and developed using four parameters/themes considered most important in producing a high power generating, yet usable device: Anode- The use of nano-engineered carbon nanomaterials, carbon nanotubes and graphene, as anode as well as testing semiconductor industry standard anode contact area materials for enhanced current production. 5 Cathode- The introduction of a membrane-less air cathode to eliminate the need for continuous chemical refills and making the entire device mobile. Reactor design- The testing of four different reactor designs (1-75 μLs) with various features intended to increase sustainability, cost-effectiveness, and usability of the microsized MFC. Fuels- The utilization of real-world fuels, such as industrial wastewaters and saliva, to power micro-sized MFCs. The micro-sized MFC can be tailored to fit a variety of applications by varying these parameters. The device with the highest power production here was designed to be an inexpensive and robust power source in applications like point-of-care diagnostics in developing countries. This 25 μL graphene nanomaterial anode, air cathode device in an inexpensive flexible rubber architecture was powered by saliva and achieved 3.55 μW/cm2 and 35.2 W/m3. The continued optimization of MFC technology promises many interesting and innovative applications.

Concerns about climate change brought about by the increasing usage of fossil fuels has made it imperative to develop sustainable energy usage based on renewable sources. Micro-hydel plants are an important source of renewable energy that can be exploited to supply requirements of local loads in remote locations while operating as an isolated source, or the larger network when operating in grid connected mode. The focus of this research is to develop an alternative topology to the one currently in use in micro-hydel power plants. While existing plants are based on a ballast-controlled, fixed-speed, operator-supervised model, the proposed work introduces a ballast-free, variable-speed generator capable of unsupervised operation. Conventional micro-hydel generators use o-the-shelf machines with the purported aim of reducing costs. They run at a fixed speed, maintaining constant electrical load by switch-ing a plant-situated ballast load to compensate for consumer load changes. Although the intention is to have a simplified control scheme and reduced costs, the conventional plants end up being expensive since the balance-of-system costs are increased. The plant re-quires supervision by a trained operator and frequent maintenance, failing which the reliability suers. The cost and maintenance reduction possible is analysed by comparing the proposed topology with a typical well designed conventional micro-hydel plant. The proposed topology takes the characteristics of the turbine into account, and by running at variable speed, ensures that only as much power is generated as required by the consumer load. This eliminates the ballast load and associated problems present in conventional plants. The generator can be connected to the grid, if present, enabling the available power to be fully utilized. The behavior of a hydraulic turbine operating at a fixed head and discharge rate with no flow control is analyzed. Based on the turbine characteristics, a generator topology is developed, which operates in a speed range dictated by the characteristics of the turbine. Continual supervision is unnecessary since the operation of the generator is within safe limits at all times. A simple emulator that can mimic the steady state and dynamic behaviour of the turbine is developed to test the proposed generator. The two-machine wound rotor generator proposed has an auxiliary exciter similar to a conventional brushless alternator with the additional provision for bidirectional power transfer. The shaft mounted rotor side electronics facilitate brushless operation, and to-gether with the stator side controllers form an embedded system that does away with having to tune the plant in-situ. The control scheme is evaluated for expected perfor-mance in dierent operating modes. The thesis also discusses an optimization of the synchronous speed of the generator with respect to the turbine characteristics. This minimizes the bidirectional slip power transfer requirements of the rotor side converters and leads to the lowest rating for the auxiliary machine. The proposed generator can then operate like a conventional synchronous gen-erator in the grid connected mode with a simplified control scheme.

Chan Ming-Ho Gordon.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2000.
Includes bibliographical references (leaves 104-105).
Abstracts in English and Chinese.
Chapter CHAPTER 1 --- INTRODUCTION --- p.1
Chapter 1.1 --- BACKGROUND ON MICRO POWER SUPPLY --- p.1
Chapter 1.1.1 --- Brief Introduction --- p.1
Chapter 1.1.2 --- Proposed Applications of Micro Power Supplies --- p.3
Chapter 1.1.3 --- Comparison Among Different Power Sources --- p.4
Chapter 1.2 --- LITERATURE SURVEY --- p.8
Chapter CHAPTER 2 --- MICRO POWER GENERATOR WITH COPPER SPRINGS --- p.10
Chapter 2.1 --- POWER PRODUCTION FROM MECHANICAL VIBRATIONS: SYSTEM ANALYSIS --- p.10
Chapter 2.2 --- DESIGN OF MICRO RESONATING SPRING --- p.16
Chapter 2.2.1 --- Design Objective --- p.16
Chapter 2.2.2 --- Material Selection --- p.18
Chapter 2.2.2.1 --- Mechanical Resonating Structure --- p.18
Chapter 2.2.2.2 --- Electromagnetic Structure --- p.23
Chapter 2.3 --- LASER MICROMACHINING OF SPRING STRUCTURE --- p.26
Chapter 2.3.1 --- Si Bulk Micromachining --- p.26
Chapter 2.3.2 --- Laser Micromachining --- p.28
Chapter CHAPTER 3 --- COMPUTER SIMULATION --- p.31
Chapter 3.1 --- TRANSIENT VOLTAGE AND POWER OUTPUT --- p.31
Chapter 3.2 --- SYSTEM RESPONSE WITH VARYING PARAMETERS --- p.35
Chapter CHAPTER 4 --- FINITE ELEMENT ANALYSIS --- p.39
Chapter 4.1 --- STRUCTURAL STATIC ANALYSIS --- p.41
Chapter 4.1.1 --- Building a Model --- p.41
Chapter 4.1.2 --- "Material, Loading And Boundary Condition" --- p.45
Chapter 4.1.3 --- Comparison Between Generator Designs --- p.46
Chapter 4.2 --- MODAL ANALYSIS AND HARMONIC RESPONSE ANALYSIS --- p.51
Chapter 4.3 --- NONLINEARITY --- p.52
Chapter CHAPTER 5 --- COMPARISON OF MODELING AND EXPERIMENTAL RESULTS --- p.55
Chapter 5.1 --- EXPERIMENT SETUP --- p.55
Chapter 5.1.1 --- Generator System --- p.55
Chapter 5.1.2 --- Vibration and Measurement --- p.60
Chapter 5.2 --- MODELING AND EXPERIMENTAL COMPARISON --- p.62
Chapter 5.2.1 --- Voltage and Power Comparison --- p.64
Chapter 5.2.2 --- Mechanical Response --- p.66
Chapter CHAPTER 6 --- SUGGESTIONS FOR POWER GENERATOR WITH RESONATING FREQUENCY BELOW 10HZ --- p.77
Chapter CHAPTER 7 --- CONCLUSION --- p.80
BIBLIOGRAPHY --- p.104

Ching Ngai-hung.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 81-83).
Abstracts in English and Chinese.
Chapter CHAPTER 1 ´ؤ --- INTRODUCTION --- p.1
Chapter 1.1 --- Background on Micro Power Supply --- p.1
Chapter 1.2 --- Literature Survey --- p.3
Chapter 1.2.1 --- Comparison Among Different Power Sources & Transduction Mechanisms --- p.3
Chapter 1.2.2 --- Previous Works in Vibration Based Generator --- p.6
Chapter CHAPTER 2 一 --- DESIGN OF THE MICRO-POWER GENERATOR --- p.8
Chapter 2.1 --- Concept of Power Generation --- p.8
Chapter 2.2 --- Design Objectives of the Micro Power Generation --- p.9
Chapter 2.3 --- System Modelling and Configuration of the Generator --- p.10
Chapter 2.4 --- RESONATING STRUCTURE --- p.13
Chapter 2.4.1 --- Material Selection --- p.13
Chapter 2.4.2 --- Fabrication Method --- p.14
Chapter CHAPTER 3 一 --- INDUCTING STRUCTURE --- p.17
Chapter 3.1 --- Selection of Winding Method --- p.17
Chapter 3.2 --- Solenoid Windings --- p.19
Chapter 3.2.1 --- Fabrication Process --- p.19
Chapter 3.3 --- PCB Windings --- p.20
Chapter 3.3.1 --- Fabrication Process of the Prototype of Six-layer PCB --- p.21
Chapter CHAPTER 4 一 --- EXPERIMENTAL RESULTS --- p.27
Chapter 4.1 --- Experimental Setup --- p.27
Chapter 4.1.1 --- Generator Systems --- p.27
Chapter 4.1.2 --- Measurement of Vibration and Output from the Generator --- p.28
Chapter 4.1.3 --- Observations of Vibration Motions --- p.31
Chapter 4.2 --- SPRING FOR THE MICRO GENERATOR --- p.32
Chapter 4.2.1 --- Spring Micromachining Optimization --- p.32
Chapter 4.2.2 --- Mode Shapes and Spiral-spring Structures --- p.35
Chapter 4.3 --- MAGNET FOR THE MICRO GENEARTOR --- p.37
Chapter 4.3.1 --- Generator Output and Magnetic Dipole Orientation --- p.37
Chapter 4.4 --- HAND-WIRED COIL GENEARTOR --- p.45
Chapter 4.4.1 --- Performance of Different Design of Housings --- p.45
Chapter 4.5 --- PCB COIL GENERATOR --- p.48
Chapter 4.5.1 --- Size of PCB Coils vs. Generator Output --- p.48
Chapter 4.5.2 --- Effect of Number of PCB Layers --- p.54
Chapter 4.5.3 --- Array of Generators --- p.61
Chapter CHAPTER 5 一 --- MODELLING AND COMPUTER SIMULATION --- p.63
Chapter 5.1 --- Modelling the Second-Order System --- p.63
Chapter CHAPTER 6 一 --- APPLICATION DEMONSTRATIONS --- p.69
Chapter 6.1 --- INFRARED SIGNAL TRANSMISSION --- p.69
Chapter 6.2 --- RF WIRELESS TEMPERATURE SENSING SYSTEM --- p.70
Chapter CHAPTER 7 ´ؤ --- CONCLUSION --- p.75
Chapter CHAPTER 8 一 --- FUTURE WORK --- p.77
BIBLIOGRAPHY --- p.81
APPENDIX --- p.84

abstract: Energy harvesting from ambient is important to configuring Wireless Sensor Networks (WSN) for environmental data collecting. In this work, highly flexible thermoelectric generators (TEGs) have been studied and fabricated to supply power to the wireless sensor notes used for data collecting in hot spring environment. The fabricated flexible TEGs can be easily deployed on the uneven surface of heated rocks at the rim of hot springs. By employing the temperature gradient between the hot rock surface and the air, these TEGs can generate power to extend the battery lifetime of the sensor notes and therefore reduce multiple batteries changes where the environment is usually harsh in hot springs. Also, they show great promise for self-powered wireless sensor notes. Traditional thermoelectric material bismuth telluride (Bi2Te3) and advanced MEMS (Microelectromechanical systems) thin film techniques were used for the fabrication. Test results show that when a flexible TEG array with an area of 3.4cm2 was placed on the hot plate surface of 80°C in the air under room temperature, it had an open circuit voltage output of 17.6mV and a short circuit current output of 0.53mA. The generated power was approximately 7mW/m2. On the other hand, high pressure, temperatures that can reach boiling, and the pH of different hot springs ranging from <2 to >9 make hot spring ecosystem a unique environment that is difficult to study. WSN allows many scientific studies in harsh environments that are not feasible with traditional instrumentation. However, wireless pH sensing for long time in situ data collection is still challenging for two reasons. First, the existing commercial-off-the-shelf pH meters are frequent calibration dependent; second, biofouling causes significant measurement error and drift. In this work, 2-dimentional graphene pH sensors were studied and calibration free graphene pH sensor prototypes were fabricated. Test result shows the resistance of the fabricated device changes linearly with the pH values (in the range of 3-11) in the surrounding liquid environment. Field tests show graphene layer greatly prevented the microbial fouling. Therefore, graphene pH sensors are promising candidates that can be effectively used for wireless pH sensing in exploration of hot spring ecosystems.
Dissertation/Thesis
Doctoral Dissertation Exploration Systems Design 2018